Hello everyone. So I am dealing with sinusoidal word problems. I know how to get the answers, the only problem is figuring out which answer to use? Like for D(t)=-21cos(2pi/29.5)+384 i got answers 0.6 hours and 11.4 hours. The official answer is 11.4 hours but I don't know how that is determined to be the answer if that makes sense.
Usually in sinusoidal word problems, either both of the answers are correct, or one of the answers is correct because of the context of the problem. For example, let's say in your problem, the graph only began after 1 hour had elapsed. That would make the 0.6 hours answer invalid, because it isn't in the domain of the question.
If you could write the entire question, then I could help you establish the contest of the question and pick the correct answer.
Also, what is the value of t, and where does it fit in the equation (to the right of the equal sign)? Because 2^pi is used in the equation, I am assuming that radians, rather than degrees, are to be used here, but 384 is such a large number that it fits better in a degrees environment.
I see that both answers you got are positive. Sometimes in a problem like this, only positive answers make sense (such as elapsed time, similar to what the earlier answer by ayesha alluded to).
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